1. Field of the Invention
The present invention relates to a method of transmitting data in the form of difference signals between subscribers which are in communication with one another by way of a bus, and an arrangement for carrying out the method.
2. Background Information
One such method and arrangement is disclosed in DE 2,953,275.C2 and corresponding U.S. Pat. No. 4,445,222. Data transmitting devices are electrically isolated by means of bus couplers and are switched to bus lines. The transmission of the data on the bus takes place, as disclosed in U.S. Pat. No. 4,445,222, in the form of difference signals.
Bus coupling circuits in bus receivers provided with hysteresis circuits are disclosed in the publication, entitled "Regelungstechnische Praxis" (Control Technology in Practice), Volume 25, 1983, No. 10, pages S61-S64 and pages S69-S70. The hysteresis circuits there serve to suppress superimposed interference, or noise, signals.
DE 3,433,150.A1 discloses a subscriber circuit for coupling a subscriber to a bus. Measures are taken there to make sure all subscribers are protected from short circuits at the interface.
In EP 89,115,672.1, corresponding to U.S. Pat. No. 4,985,903, it is proposed to create a bus coupling circuit with fault tolerance for the transmission of unipolar signals by providing each bus driver with an additional hysteresis circuit in order to re-introduce a d.c. voltage value at the point free of direct current where the bus driver is coupled to the bus.